The invention relates to a magnetic head for detecting information-representing magnetic fields on a magnetic recording medium movable relatively with respect to the magnetic head. The head is of a type comprising an elongate magnetoresistive element which at two oppositely located ends had contacts for the connection to a source of measuring current. The element has a magnetic anisotropy and the easy direction magnetization is parallel to the longitudinal axis of the element. The element comprises at least one electrically readily conductive strip which is provided obliquely on a surface of the element at an angle of at least 30.degree. and at most 60.degree. with the longitudinal axis of the element.
The invention relates to magnetic reading heads destined in particular, but not exclusively, for detecting magnetic fields in magnetic recording media, for example, magnetic tapes or disks.
A magnetic head of the kind mentioned in the preamble is known from Philips Technical Review 37, pp. 42-50, 1977, No. 2/3. In the known head, one or more oblique conductive strips are provided on one of the surfaces of the magnetoresistive element, preferably at an angle of 45.degree. with the longitudinal axis of the element. These strips serve as equipotential strips so that the direction of the current in the element which is at right angles to the equipotential strips encloses an angle with the easy direction of magnetization, preferably an angle of 45.degree.. In this manner the operation of the known magnetic head is linearized: the relative resistance variation of the magnetoresistive element (.DELTA.R/R) as a function of the transversal external magnetic field (H), which is presented by a magnetic recording medium to be read is then represented as a matter of fact by a substantially linear odd function.
Although the known head has the advantage of a simple linearization, it has the disadvantage, however, that a certain deviation from the linear characteristic occurs as a result of the condition that near the edges of the magnetoresistive element extending in the longitudinal direction the angle at which the current flows with respect to the longitudinal axis varies until the angle becomes 0.degree. at the boundary of the element. The result of this is that in fact the playback characteristic of the known magnetic head is not represented by an odd function but by the sum of an odd function and an even function.
Copending U.S. application Ser. No. 31,259 filed Apr. 18, 1979 relates to magnetic head of the above type which does not exhibit this disadvantage. To that end it includes two components of a magnetically permeable material (so called flux conduxtors) positioned in line with each other, between which components a gap is present, the magnetoresistive element spanning said gap, the facing ends of the components of magnetically permeable material covering the edge zone of the magnetoresistive element extending parallel to the longitudinal axis of the element, the end of the first one of the components of magnetically permeable material remote from the magnetoresistive element being adapted to cooperate with a magnetic recording medium.
In this manner it is ensured that the edge zones of the magnetoresistive element extending parallel to the longitudinal axis are shortcircuited magnetically by the magnetically permeable components, Since now substantially no magnetic flux originating from the recording medium flows through the edge zones, the contribution of their resistance variation to the overall resistance variation of the element is very small and hence also the non-linearity caused by the edge zones so that the playback characteristic has a much more linear variation than that of the known magnetic head.
A geometric arrangement of a magnetoresistive element as a bridge of a gap between two magnetically permeable elements is known per se from U.S. Pat. No. 3,921,217. However, the magnetoresistive element disclosed in the latter patent is not of the kind to which the invention relates, but of a magnetically biased type in which it is necessary to apply a permanent magnetic field for the lineariza of the playback characteristic of the magnetoresistive element so as to displace the workpoint to a linear area of the curve resistance/magnetic field. However, in a magnetic head having such a magnetoresistive element the problem for which the invention provides a solution does not occur.
Although the distortion of a current-biased magnetoresistive element with magnetically short-circuited edge zones disclosed in the above copending application is already considerably less than of a similar element the edge zones of which are not magnetically shortcircuited, some distortion may nevertheless remain. This appears to be due to the condition that the magnetoresistive head according to the invention is supersensitive to long-wavelength signals.